This invention relates to an improved process for the preparation of acetylsulfaguanidine. More particularly this invention relates to a continuous process for the preparation of acetylsulfaguanidine from ammonium acetylsulfanilylcyanamide.
The transformation of ammonium acetylsulfanilylcyanamide (AASC) to acetylsulfaguanidine (ASG) is illustrated by the following reaction: ##STR1##
ASG is a well-known compound which is convertible into sulfaguanidine, an important chemotherapeutic agent, useful in the treatment of various intestinal infections. Sulfaguanidine is particularly valuable for such use since it is not readily absorbed from the gastrointestinal tract, thus minimizing toxicity. It is also useful as an intermediate for the synthesis of other chemotherapeutic agents.
Mosnier in Example 2 of U.S. Pat. No. 2,463,793 discloses a process wherein a 50% aqueous solution of AASC is transformed to ASG by autoclaving at 150.degree.-155.degree. C. for 2 hours, cooling the reaction mixture and collecting the insoluble ASG by filtration. However, the yields obtained in this process are low.
In Example 1 of Mosnier a process is disclosed wherein AASC is crystallized from aqueous solution and the crystalline salt is converted to ASG by heating at 150.degree.-170.degree. C. The resulting melt congeals to a solid mass. However, in this process the yield of crystalline AASC obtained is low because of high solubility in water and the crystals obtained contain water of hydration which cannot be readily removed by drying. Also, the crystals obtained cannot be uniformly heated without splashing or bubbling occurring. Furthermore, the AASC congeals into a solid mass of ASG which is difficult to handle.
There is a need for an improved process wherein concentrated aqueous solutions of AASC can be converted to ASG in higher yields and which avoids the processing of congealed ASG.